U.S. patent number 9,214,884 [Application Number 14/242,160] was granted by the patent office on 2015-12-15 for motor driving device and brushless motor.
This patent grant is currently assigned to PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.. The grantee listed for this patent is Panasonic Corporation. Invention is credited to Yasushi Kato, Mitsuhiro Sakamoto, Daisuke Sonoda, Yasuyuki Yokouchi.
United States Patent |
9,214,884 |
Sonoda , et al. |
December 15, 2015 |
Motor driving device and brushless motor
Abstract
A motor driving device of the present invention is a motor
driving device that incorporates so-called vector control of
controlling a current applied to a motor winding in accordance with
the position of a rotor. The motor driving device receives the
input of a duty command value from a host controller via a command
input port, for example. The motor driving device obtains a current
command or a speed command as a command value such that the input
duty command value is equal to the duty of a drive pulse output
from an inverter. Then, the motor driving device performs vector
control based on the obtained command value.
Inventors: |
Sonoda; Daisuke (Osaka,
JP), Kato; Yasushi (Kyoto, JP), Yokouchi;
Yasuyuki (Osaka, JP), Sakamoto; Mitsuhiro (Osaka,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Corporation |
Kadoma-shi, Osaka |
N/A |
JP |
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Assignee: |
PANASONIC INTELLECTUAL PROPERTY
MANAGEMENT CO., LTD. (Osaka, JP)
|
Family
ID: |
51672157 |
Appl.
No.: |
14/242,160 |
Filed: |
April 1, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140306626 A1 |
Oct 16, 2014 |
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Foreign Application Priority Data
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Apr 11, 2013 [JP] |
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2013-082733 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02P
21/22 (20160201) |
Current International
Class: |
H02P
21/00 (20060101); H02P 6/00 (20060101) |
Field of
Search: |
;318/400.02 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2001-292589 |
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Oct 2001 |
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JP |
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2004-040906 |
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Feb 2004 |
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JP |
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2007/132889 |
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Nov 2007 |
|
WO |
|
Primary Examiner: Glass; Erick
Attorney, Agent or Firm: Hamre, Schumann, Mueller &
Larson, P.C.
Claims
What is claimed is:
1. A motor driving device which receives a duty command value for
commanding a duty of a drive pulse for driving a motor winding and
generates the drive pulse having the duty pulse according to the
duty command value that is input, the motor driving device
comprising: a command input port configured to be input the duty
command value; a command generator configured to generate a current
command value which corresponds to current amount for energizing
the motor winding by using the duty command value that is input to
the command input port; a current controller configured to generate
a voltage command value for applying to the motor winding on the
basis of current vector control system that separates a current of
the motor winding into a d-axis current and a q-axis current which
are orthogonal to each other in accordance with the current command
value; and an inverter configured to apply the drive pulse, the
drive pulse being PWM modulated at the duty according to the
voltage command value, to the motor winding.
2. The motor driving device according to claim 1, wherein the
command generator generates the current command value based on a
voltage deviation between an output voltage and a voltage command,
the output voltage obtained based on the voltage command value and
the voltage command obtained based on the duty command value.
3. The motor driving device according to claim 2, wherein the
command generator obtains a speed command value based on the
voltage deviation, obtains a speed deviation between a detected
motor speed and the speed command value, and generates the current
command value based on the speed deviation.
4. The motor driving device according to claim 2, wherein the
command generator generates the current command value by addition
of a value based on the voltage deviation, to a current value
calculated from a model of a motor equivalent circuit.
5. The motor driving device according to claim 1, wherein the drive
pulse having the duty according to the duty command value is
generated by feedback control such that a deviation between the
input duty command value and the duty of the drive pulse becomes
zero.
6. The motor driving device according to claim 1, wherein the
command generator generates the current command value by
calculation from a model of a motor equivalent circuit.
7. A brushless motor comprising the motor driving device according
to claim 1.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor driving device for
rotationally driving a brushless motor.
2. Description of the Related Art
In brushless motors for household electric appliances such as fan
motors for air-conditioners, a motor incorporating a motor driving
device inside the motor is recently put into practical use. The
motor driving device includes circuit components such as an
inverter, a CPU (central processing unit), and a position sensor
such as a hall element. In such a configuration, the CPU generates
a switching signal to the inverter, and a motor winding is
energized with a rectangular wave voltage or a sine wave voltage.
Thus, the motor driving device drives the motor.
A host controller for controlling the motor driving device adjusts
a duty command input to the motor driving device such that speed,
air quantity or the like becomes a desired value, on a basis of a
signal indicating the actual number of rotations, which is received
from the side of the motor driving device, or the like.
FIG. 9 is a block diagram showing a configuration example of such
conventional motor driving device 98. After AC power supply 11 is
rectified by rectifier circuit 21 to be smoothed through smoothing
capacitor 22, the DC voltage is supplied to three-phase inverter 23
included in motor driving device 98. Inverter 23 converts the DC
voltage into an arbitrary AC voltage, and the converted AC voltage
is supplied to motor 19. Position sensor 32 detects the position of
a rotor of motor 19 to output this position as position detection
signal Ps. Position detection signal Ps is supplied to position
detector 34, the position of the rotor is computed to be supplied
to FG output unit 54 as motor position signal Pd. FG output unit 54
outputs FG pulse signal FG indicating actual motor speed, on the
basis of motor position signal Pd.
Additionally, FG pulse signal FG is supplied from FG output unit 54
to host speed controller 51 on the side of host controller 12. Host
speed controller 51 adjusts duty command value D* such that speed,
air quantity or the like becomes a desired value, based on FG pulse
signal FG, to output adjusted duty command value D* to motor
driving device 98.
Motor driving device 98 supplies, to voltage controller 57, duty
command value D* received from host controller 12. Voltage
controller 57 obtains values of three-phase voltage command values
V.sub.u*, V.sub.v* and V.sub.w*, from input duty command value D*
and motor position signal Pd, to output the obtained values to PWM
controller 59. PWM controller 59 generates a switching signal
obtained by arranging pulses with duty according to the values of
voltage command value V.sub.u*, V.sub.v* and V.sub.w* in time
series. Then, inverter 23 applies drive pulses Uo, Vo and Wo with
duty according to this switching signal to the motor winding. By
such operation, rectangular wave voltages or sine wave voltages are
artificially generated from drive pulses Uo, Vo and Wo on the basis
of pulse-width modulation (PWM), to be applied to the motor
windings, thereby driving motor 19.
As a configuration example of such a motor driving device, for
example, Unexamined Japanese Patent Publication No. 2001-292589
discloses a fan motor having a configuration in which an inverter
is driven by drive pulses according to a duty command.
As a higher performance control system than rectangular wave drive
system in which rectangular wave voltages are applies, or a sine
wave drive system in which sine wave voltages are applied,
described above, there is widely known a so-called vector control
system in which a motor winding current is controlled in accordance
with the position of a rotor. In vector control, a current in a
magnet torque direction (q-axis current) that is generated by
permanent magnets, and a current in a magnetic flux direction
(d-axis current) that is generated by permanent magnets can be
independently controlled. Therefore, it is possible to implement
high efficiency, low noise, and high speed response, compared to
the rectangular wave drive system or the sine wave drive
system.
As a configuration example of a motor driving device using such a
vector control system, for example, Unexamined Japanese Patent
Publication No. 2004-40906 discloses a vector control device of a
synchronous motor.
FIG. 10 is a block diagram of conventional motor driving device 99
that is configured to control motor speed by such vector control.
Conventional motor driving device 99 shown in FIG. 10 also has a
configuration in which motor 19 is driven by inverter 23. In FIG.
10, motor position signal Pd is supplied to differentiator 60.
Differentiator 60 computes the speed of a rotor by differentiation
of this motor position signal Pd. The speed thus computed is
supplied to speed controller 56 as motor speed signal Sp indicating
the actual speed of the rotor.
Speed controller 56 computes current command value I* from speed
command value Sp* and motor speed signal Sp. Current controller 53
obtains three-phase voltage command values v.sub.u*, v.sub.v* and
v.sub.w* from current command value I*, current detection signal Id
indicating the winding current of a motor detected from current
detector 31, and motor position signal Pd, to output three-phase
voltage command values v.sub.u*, v.sub.v* and v.sub.w* to PWM
controller 59. Herein, current controller 53 has a configuration
based on the vector control system, and in current controller 53, a
current is separated into a q-axis current in a torque direction
and a d-axis current in a direction orthogonal to the torque
direction for processing. Then, current controller 53 receives a
current command for setting a current to current command value I*,
and computes voltage command values v.sub.u*, v.sub.v* and v.sub.w*
for supplying power to the motor windings.
Conventional motor driving device 99 shown in FIG. 10 attains high
efficiency, low noise, and high speed response, as a configuration
in which such a vector control system is used.
However, in a case where it is intended to introduce the vector
control as it is, it is necessary to control by use of such a
current command as to set the current to current command value I*
like conventional motor driving device 99 shown in FIG. 10.
Therefore, for example, in a case where the vector control is
introduced to the configuration shown in FIG. 9, it is necessary to
change a current command from the side of a host unit from a duty
command to a current command, thereby causing a problem that not
only a motor driving device but also a host controller are required
to be changed.
In Unexamined International Patent Publication No. 2007/132889,
when the vector control is introduced, an inverter circuit inside a
motor is moved onto an external indoor control board, the
generation of a switching signal that has performed by a CPU inside
the motor is performed by a microcomputer on the indoor control
board, which requires significant change.
SUMMARY OF THE INVENTION
A motor driving device of the present invention is a motor driving
device that incorporates so-called vector control of controlling a
current applied to a motor winding in accordance with the position
of a rotor. The motor driving device obtains a current command or a
speed command as a command value such that the input duty command
value is equal to the duty of drive pulses output from an inverter.
Then, the motor driving device performs vector control based on the
obtained command value. According to the motor driving device, it
is possible to control the output duty of the inverter to duty
desired by the host controller during vector control.
Consequently, it is possible to provide a motor driving device for
a brushless motor incorporating vector control, only by the change
of a motor control circuit unit without the change of the host
controller.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a block diagram of a configuration including a motor
driving device according to First Exemplary Embodiment of the
present invention;
FIG. 2 is a sectional view of a brushless motor incorporating the
motor driving device according to the present invention;
FIG. 3 is a block diagram showing detailed configurations of a
current command calculator and a current controller according to
First Exemplary Embodiment of the present invention;
FIG. 4 is a block diagram of a configuration including a motor
driving device according to Second Exemplary Embodiment of the
present invention;
FIG. 5 is a block diagram showing detailed configurations of a
speed command calculator, a speed controller, and a current
controller according to Second Exemplary Embodiment of the present
invention;
FIG. 6 is a block diagram showing detailed configurations of a
current command calculator and a current controller according to
Third Exemplary Embodiment of the present invention;
FIG. 7 is an equivalency circuit diagram of a brushless motor;
FIG. 8 is a block diagram showing detailed configurations of a
current command calculator and a current controller according to
Fourth Exemplary Embodiment of the present invention;
FIG. 9 is a block diagram of a configuration including a
conventional motor driving device; and
FIG. 10 is a block diagram of a conventional motor driving device
in a case where motor speed is controlled by vector control.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, Exemplary Embodiments of the present invention are
described with reference to the drawings. The present invention is
not limited by these Exemplary Embodiments.
First Exemplary Embodiment
FIG. 1 is a block diagram of a motor driving system including
brushless motor 101 provided with motor driving device 111
according to First Exemplary Embodiment of the present invention.
Motor driving device 111 is configured to perform vector control by
use of a current command obtained from a duty command.
As shown in FIG. 1, a motor driving system in this Exemplary
Embodiment includes brushless motor 101, and host controller 12
that controls this brushless motor 101. In this Exemplary
Embodiment, brushless motor 101 is mounted with circuit components
that function as motor driving device 111. That is, as shown in
FIG. 1, in brushless motor 101, motor driving device 111
rotationally drives motor 19.
In FIG. 1, after AC power supply 11 is rectified by rectifier
circuit 21 to be smoothed through smoothing capacitor 22, the DC
voltage is supplied to three-phase inverter 23 included in motor
driving device 111. Three-phase inverter converts the DC voltage
into an arbitrary AC voltage, and the converted AC voltage is
supplied to motor 19. In this Exemplary Embodiment, motor 19 is
thus driven in three phases, namely, a U phase, a V phase, and a W
phase that are different from each other by 120 degrees.
FIG. 2 is a sectional view showing a configuration example of motor
19 in this Exemplary Embodiment. As shown in FIG. 2, motor 19
includes rotor 19r and stator 19s. Rotor 19r has permanent magnets
19r2 about shaft 19r1. Stator 19s is configured such that motor
windings 19c are wound around stator cores 19s1.
Furthermore, in this Exemplary Embodiment, as described above,
brushless motor 101 is configured such that circuit components 191
that function as motor driving device 111 are incorporated in motor
19. These circuit components 191 are mounted on circuit board 192,
and position sensor 32 is also mounted on circuit board 192 in
order to detect the rotational position of rotor 19r, for example.
In such a structure, motor windings 19c are energized and driven by
AC power, so that rotor 19r is rotatably supported by bearing 193
to rotate. Furthermore, position sensor 32 detects the position of
rotor 19r to output, to motor driving device 111, position
detection signal Ps indicating the detected position.
Host controller 12 is included in, for example, an apparatus
mounted with brushless motor 101, or the like, and controls the
operation of brushless motor 101, or the like. In order to perform
such control, host controller 12 includes host speed controller 51
that is configured by a CPU (Central Processing Unit), a DSP
(Digital Signal Processor), or the like. Motor driving device 111
is notified of a command for rotationally controlling motor 19,
from such host speed controller 51 via a signal transmission line.
FG pulse signal FG indicating the actual number of rotations is
supplied to host speed controller 51 from motor driving device
111.
In this Exemplary Embodiment, as a command from host controller 12,
duty command value D* for commanding the duty of drive pulses
applied to motor windings 19c on the basis of PWM modulation of the
inverter is notified to command input port 14 of motor driving
device 111. That is, host speed controller 51 adjusts duty command
value D* such that speed, air quantity or the like is a desired
value based on FG pulse signal FG, to control the rotation in motor
19. Herein, the duty means the ratio of a pulse width to a pulse
periodic width in a pulse signal such as a drive pulse. For
example, when duty command value D* indicates 90%, a drive pulse
whose pulse width is 90% in one period is output.
A configuration of motor driving device 111 is now described. Motor
control device 111 includes current command calculator 52, current
controller 53, PWM controller 59, inverter 23, position detector
34, and FG output unit 54. As described above, sensor signal Ps is
supplied to motor driving device 111 from position sensor 32
arranged on motor 19.
In motor driving device 111, sensor signal Ps is supplied to
position detector 34. Position detector 34 computes the position of
rotor 19r by use of this sensor signal Ps, to output the computed
position as motor position signal Pd. Motor position signal Pd is
supplied to FG output unit 54 and current controller 53. FG output
unit 54 generates FG pulse signal FG that is a signal indicating
the actual number of rotations of motor 19, on the basis of this
motor position signal Pd. Herein, FG pulse signal FG is a pulse
signal of a frequency proportional to the number of rotations of a
motor, which is called an FG signal. This FG pulse signal FG is
transmitted to host controller 12.
The duty command value D* notified from host controller 12 is
supplied to current command calculator 52 via command input port
14. Current command calculator 52 computes current command value I*
such that the duty of drive pulses Uo, Vo and Wo output from
inverter 23 becomes duty indicated by duty command value D* input
from the side of host controller 12. That is, current command
calculator 52 functions as a command generator that generates a
command value such that duty command value D* and the duty of drive
pulses Uo, Vo and Wo are equal, and generates current command value
I* that is a current command as a command value.
Current controller 53 obtains voltage command values Vu*, Vv* and
Vw* from current command value I*, motor winding current value Idet
detected from current detector 31, and motor position signal Pd
computed from position detector 34, to output the obtained voltage
command values to PWM controller 59.
PWM controller 59 generates respective voltage command signals
corresponding to voltage command values Vu*, Vv* and Vw* supplied
from current controller 53 in respective phases. Then, PWM
controller 59 applies pulse-width modulation to the generated
voltage command signals as respective modulation signals, to output
the modulated signals as drive pulse signals PWu, PWv and PWw
configured in a pulse train to which pulse-width modulation is
applied.
Inverter 23 energizes motor windings 19c for respective phases on
the basis of drive pulse signals PWu, PWv and PWw, to drive motor
windings 19c. Inverter 23 includes switching elements on the sides
of a positive electrode and a negative electrode of a power supply,
for each phase. When the switching elements are turned on/off by
the pulse timing of drive pulse signals PWu, PWv and PWw, drive
pulses Uo, Vo and Wo are supplied from respective drive outputs to
motor windings 19c via the switching elements of ON from the power
supply. Herein, in this Exemplary Embodiment, assuming that the
duty of drive pulses Uo, Vo and Wo is duty D, feedback control is
performed such that duty D becomes duty command value D*.
Therefore, inverter 23 in this Exemplary Embodiment energizes and
drives motor windings 19c with drive pulses Uo, Vo and Wo with the
duty of duty command value D*. Considered from a different angle,
drive pulses Uo, Vo and Wo are signals to which pulse-width
modulation is applied by voltage command signals, and therefore
inverter 23 in this Exemplary Embodiment equivalently supplies
respective drive voltages corresponding to voltage command values
Vu*, Vv* and Vw* to motor windings 19c, to energize and drive motor
windings 19c.
Current command calculator 52 and current controller 53 are now
described in more detailed. FIG. 3 is a block diagram showing
detailed configurations of current command calculator 52 and
current controller 53 according to this Exemplary Embodiment. In
this Exemplary Embodiment, current command calculator 52 is
configured as shown in FIG. 3, so that current command value I*
supplied to current controller 53 is computed such that a
difference between duty command value D* and the duty of drive
pulses Uo, Vo and Wo that is the actual output of inverter 23
becomes zero.
The relation between amplitude V.sub.ph.sub.--amp of a phase
voltage, and d-axis voltage v.sub.d and q-axis voltage v.sub.q is
expressed by the following (Expression 1).
.times..times..times. ##EQU00001##
Assuming that a voltage utilization factor is denoted by .eta., and
the carrier wave amplitude of inverter 23 is denoted by
CARRIER_COUNT, the relation between amplitude
V.sub.ph.sub.--.sub.amp of the phase voltage and duty D by the
switching of inverter 23 is expressed by the following (Expression
2).
.eta..times..times..times..times. ##EQU00002##
Voltage utilization factor .eta. is determined by the modulation
system of inverter 23. In a case of a three-phase modulation
system, voltage utilization factor .eta. is about 0.87. In a case
of a two-phase modulation system or a triple harmonics injection
system of superimposing harmonics according to the variation of the
center value between upper and lower envelopes of carrier waves in
three-phase modulation, voltage utilization factor .eta. is 1.
Herein, d-axis voltage command v.sub.d* and q-axis voltage command
v.sub.q* that are the operation amount of current controller 53 are
substituted for (Expression 1), so that output voltage V
corresponding to an actual voltage during operation at the present
time can be obtained. In FIG. 3, such output voltage V is obtained
by output voltage calculator 523.
Duty command value D* is substituted for (Expression 2), so that
voltage command V* corresponding to duty command value D* can be
obtained. In FIG. 3, such voltage command V* is obtained by voltage
command calculator 521.
In this Exemplary Embodiment, feedback control is performed such
that a deviation between voltage command V* and output voltage V
thus obtained becomes zero, thereby computing current command value
I* for performing vector control. That is, current command
calculator 52 is thus configured, so that current command value I*
for performing the vector control is obtained from duty command
value D*. As shown in FIG. 3, current command calculator 52 causes
subtracter 524 to operate the difference between voltage command V*
and output voltage V, to obtain deviation dV. Then, current command
calculator 52 outputs a value obtained by performing a PI
(Proportional, Integral) process to deviation dV with PI operation
unit 522, as current command value I*.
Current controller 53 has a configuration based on the vector
control system, in current controller 53, a current is separated
into a q-axis current in a torque direction and a d-axis current in
a direction orthogonal to the torque direction for processing. In
order to perform such vector control, in current controller 53,
current coordinate converter 531 computes d-axis current command
value i.sub.d* and q-axis current command value i.sub.q* of two
phases, from current command value I* supplied from current command
calculator 52. Additionally, current controller 53 computes d-axis
motor winding current value i.sub.d and q-axis motor winding
current value i.sub.q of two phases, from current Idet detected
from current detector 31. Then, subtracter 532 obtains deviation
di.sub.d between d-axis current command value i.sub.d* and d-axis
motor winding current value i.sub.d, and PI operation unit 534
performs a PI process to deviation di.sub.d, to output deviation
di.sub.d as d-axis voltage command v.sub.d*. Additionally,
subtracter 533 obtains deviation di.sub.q between q-axis current
command value i.sub.q* and q-axis motor winding current value
i.sub.q, and PI operation unit 535 further performs a PI process to
deviation di.sub.q, to output deviation di.sub.q as q-axis voltage
command v.sub.q*. Thus, current controller 53 performs feedback
control such that a deviation between d-axis current command value
i.sub.d* and d-axis motor winding current value i.sub.d, and a
deviation between q-axis current command value i.sub.q* and q-axis
motor winding current value i.sub.q each become zero, on the basis
of the vector control, to compute d-axis voltage command value
v.sub.d* and q-axis voltage command value v.sub.q*. Current
controller 53 causes voltage coordinate converter 536 to perform
rotational coordinate transformation and two-phase-three-phase
conversion to d-axis voltage command value v.sub.d* and q-axis
voltage command value v.sub.q*. Thus, voltage command values
V.sub.u*, V.sub.v* and V.sub.w* of three phases are computed. As
described above, inverter 23 applies drive pulses Uo, Vo and Wo
with duty corresponding to such voltage command values Vu*, Vv* and
Vw*, to respective motor windings 19c, thereby energizing and
driving motor windings 19c.
As described above, in this Exemplary Embodiment, the feedback
control of current command value I* is performed such that a
difference between duty command value D* and the duty of drive
pulses that is the actual output of the inverter becomes zero,
thereby computing current command value I* from duty command value
D*. Consequently, according to this Exemplary Embodiment, it is
possible to perform the rotation control of a motor on the basis of
duty control using duty command value D* with high efficiency, low
noise, and high speed response as a configuration in which a vector
control system is used. Therefore, it is possible to provide a
motor driving device for a brushless motor incorporating vector
control, only by the change of a motor control circuit unit.
Second Exemplary Embodiment
FIG. 4 is a block diagram of a motor driving system including
brushless motor 102 provided with motor driving device 112
according to Second Exemplary Embodiment of the present invention.
Herein, motor driving device 112 is configured to perform vector
control by use of a speed command obtained from duty command value
D*. Second Exemplary Embodiment is different from First Exemplary
Embodiment in that current command calculator 52 is changed to
speed command calculator 55 and speed controller 56. In FIG. 4, the
same components as those in FIG. 1 are denoted by the same
reference numerals, and detailed description of these components
are omitted. FIG. 5 is a block diagram showing detailed
configurations of speed command calculator 55 and speed controller
56 according to this Exemplary Embodiment.
In FIG. 4, speed command calculator 55 computes speed command value
.omega.* such that the duty of drive pulses Uo, Vo and Wo output
from inverter 23 becomes duty command value D* input from the side
of host controller 12. Speed command value .omega.* by speed
command calculator 55 is computed by the same configuration as that
of current command calculator 52 described in First Exemplary
Embodiment. That is, speed command calculator 55 computes speed
command value .omega.* by feedback control such that deviation dV
between output voltage V computed from (Expression 1) and voltage
command V* computed from (Expression 2) becomes zero, as shown in
FIG. 5. In this Exemplary Embodiment, this speed command calculator
55 functions as a command generator that generates a command value
such that duty command value D* and the duty of drive pulses Uo, Vo
and Wo are equal, and generates speed command value .omega.* that
is a speed command as a command value.
As the configuration of speed command calculator 55, as shown in
FIG. 5, speed command calculator 55 causes subtracter 554 to
operate a difference between output voltage V obtained by output
voltage calculator 553 and voltage command V* obtained by voltage
command calculator 551, to obtain deviation dV. Then, speed command
calculator 55 outputs a value obtained by performing a PI process
to deviation dV with PI operation unit 552, as speed command value
.omega.*.
Speed controller 56 computes current command value I*, from input
speed command value .omega.*, and motor speed .omega. corresponding
to the actual speed of the motor, which is obtained by differential
of motor position signal Pd of position detector 34 by
differentiator 60. That is, speed controller 56 performs feedback
control such that deviation d.omega. between input speed command
value .omega.* and motor speed .omega. becomes zero, and outputs
the operation amount of speed control as current command value I*
to current controller 53. As the configuration of speed controller
56, as shown in FIG. 5, speed controller 56 causes subtracter 561
to operate a difference between speed command value .omega.* and
motor speed .omega., to obtain deviation d.omega.. Then, a value
obtained by performing a PI process to deviation d.omega. with PI
operation unit 562 is output as current command value I*.
Current command value I* thus obtained is supplied to current
controller 53 that has a configuration based on a vector control
system. Similarly to First Exemplary Embodiment, inverter 23
applies drive pulses Uo, Vo and Wo with duty corresponding to
voltage command values Vu*, Vv* and Vw* calculated by current
controller 53, to respective motor windings 19c, thereby energizing
and driving motor windings 19c.
For example, in a case where the upper limit of the speed is
desired to be set not only on the host controller side but also on
the control circuit side of the motor, as a protection function of
the motor, it is difficult to implement the setting of the upper
limit of the speed also on the control circuit side in First
Exemplary Embodiment in which the speed controller is not included.
On the contrary, the motor driving device is configured to have
such a configuration as the configuration of this Exemplary
Embodiment, so that the setting of the upper limit of the speed on
the control circuit side can be easily implemented by the
restriction of generated speed command value .omega.*.
Third Exemplary Embodiment
FIG. 6 is a block diagram showing a configuration of current
command calculator 52 of a motor driving device according to Third
Exemplary Embodiment of the present invention. Third Exemplary
Embodiment is different from First Exemplary Embodiment in a
configuration in which current command value I* is computed in
current command calculator 52. In this Exemplary Embodiment, unlike
First Exemplary Embodiment, current command value I* is not
obtained by feedback control, but computed by calculation from a
reverse model of motor 19.
FIG. 7 is an equivalency circuit diagram of motor 19. Herein, v
denotes a voltage applied to motor windings 19c, i denotes a
current that flows through motor windings 19c, L denotes the
inductance of motor windings 19c, R denotes the resistance of motor
windings 19c, and e denotes an induced voltage by permanent magnets
of motor 19. From FIG. 7, the voltage equation of motor 19 can be
expressed by the following (Expression 3).
.times.dd.times..times. ##EQU00003##
In a case where (Expression 3) is considered with an effective
value, (Expression 3) can be expressed by the following (Expression
4). V.sub.rms= {square root over
(R.sup.2+(L.omega..sub.e).sup.2)}.times.I.sub.rms+K.sub.e.omega..sub.m
(Expression 4)
Herein, Vrms denotes the effective value of the voltage applied to
motor windings 19c, I.sub.rms denotes the effective value of the
current that flows through motor windings 19c, .omega., denotes an
electrical angle frequency, .omega..sub.m denotes a mechanical
angular frequency, and K.sub.e denotes an induced voltage
constant.
The relation between a winding voltage and a power supply voltage
can be expressed by the following (Expression 5). {square root over
(2)}.times.V.sub.rms=.eta..times.V.sub.dc.times.D (Expression
5)
Herein, V.sub.dc denotes a power supply voltage input to inverter
23, and is equal to the amplitude of an AC voltage applied by AC
power supply 11. The following (Expression 6) is obtained by
(Expression 4) and (Expression 5).
.times..times..omega..times..times..eta..times..times..times..omega..time-
s..times. ##EQU00004##
The relation between d-axis motor winding current value i.sub.d and
q-axis motor winding current value i.sub.q can be expressed by the
following (Expression 7).
.times..times..times..times. ##EQU00005##
Duty command value D* input from the host controller is substituted
for (Expression 6) and (Expression 7), so that current command
value I* can be computed from duty command value D*. That is, in
this Exemplary Embodiment, as shown in FIG. 6, current command
value I* is computed on the basis of the following (Expression
8).
.times..times..omega..times..times..eta..times..times..times..times..omeg-
a..times..times. ##EQU00006##
Compared to First Exemplary Embodiment in which current command
value I* is computed by feedback control, in this Exemplary
Embodiment, current command value I* is obtained by calculation as
described above. Therefore, high responsiveness is obtained, but
the obtained value is influenced by an error of a resistance value
or the like which is used in calculation.
Fourth Exemplary Embodiment
FIG. 8 is a block diagram showing a configuration of current
command calculator 52 of a motor driving device according to Fourth
Exemplary Embodiment of the present invention. Fourth Exemplary
Embodiment is different from First Exemplary Embodiment in that a
configuration, in which current command value I* is obtained from
duty command value D* by the feedback control of the present
invention, and a configuration, in which current command value I*
is obtained by calculation from a reverse model of a motor, are
combined. In this Exemplary Embodiment, a value obtained by adding
current command value I.sub.1* obtained by feedback control such
that a difference between duty command value D* described in First
Exemplary Embodiment and actual output duty D of an inverter
becomes zero, to current command value I.sub.2* obtained from the
reverse model of the motor described in Third Exemplary Embodiment
is defined as current command value I*, and vector control is
performed. This system is so-called two-degree-of-freedom control,
and enables both of high responsiveness by the use of a reverse
model, and the compensation of the influence of a modeling error by
feedback control.
As described above, according to the present invention, in a motor
driving device for a brushless motor that performs rectangular wave
drive or sine wave drive, vector control that is a control system
with higher performance can be introduced only by the change of a
motor control circuit unit without the change of the design of a
host controller, and the present invention can be utilized
generally for motor driving devices for a brushless.
* * * * *